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Previously, a stable cell suspension of cucumber tolerant to 100 µM CdCl2 was obtained (Gzyl & Gwóźdź, 2005, Plant Cell Tissue Organ Cult 80: 59-67). In this study, the relationship between the activity of antioxidant enzymes and cadmium tolerance of cucumber cells was analyzed. A cadmium-sensitive and the cadmium-tolerant cell lines were exposed to 100 µM and 200 µM CdCl2 and the activities of superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APOX) and guaiacol peroxidase (POX) were determined. In the sensitive cell line, a decrease of total activity of SOD and POX was observed, whereas the activity of CAT and APOX significantly increased in metal-supplemented medium. By contrast, in the tolerant cells, the total activity of antioxidant enzymes decreased (SOD, CAT) or was maintained at approximately the same level (APOX, POX). Moreover, a different pattern of isoenzyme activity was observed in the tolerant and sensitive cells. These results suggest that an enhanced activity of antioxidant enzymes is not directly involved in the increased tolerance to cadmium of the selected cucumber cell line.
The cadmium (Cd²⁺) and lead (Pb²⁺)-induced changes in Cu,Zn-SOD gene expression on the level of mRNA accumulation and enzyme activity were analyzed in roots of soybean (Glycine max) seedlings. The Cd²⁺ caused the induction of copper–zinc superoxide dismutase (Cu,Zn-SOD) mRNA accumulation, at each analyzed metal concentration (5–25 mg/l), whereas in Pb²⁺-treated roots this effect was observed only at the medium metal concentrations (50–100 mg/l of Pb²⁺). The analysis of Cu,Zn-SOD activity proved an increase in enzyme activity during Cd²⁺/Pb²⁺ stresses, however in Pb²⁺-treated plants the activity of enzyme was not correlated with respective mRNAs level. Presented data suggest that different metals may act on various level of Cu,Zn-SOD expression in plants exposed to heavy metals stress.
Cadmium (Cd), similarly to other heavy metals, inhibits plant growth. We have recently showed that Cd2+ either stimulates (1–4 uM) or inhibits ( 6 uM) growth of soybean (Glycine max L.) cells in suspension culture (Sobkowiak & Deckert, 2003, Plant Physiol Biochem. 41: 767–72). Here, soybean cell suspension cultures were treated with various concentrations of Cd2+ (1–10 uM) and the following enzymes were analyzed by native electrophoresis: superoxide dismutase (SOD), catalase (CAT), peroxidase (POX) and ascorbate peroxidase (APOX). We found a significant correlation between the cadmium-induced changes of soybean cell culture growth and the isoenzyme pattern of the antioxidant enzymes. The results suggest that inhibition of growth and modification of antioxidant defense reactions appear in soybean cells when Cd2+ concentration in culture medium increases only slightly, from 4 to 6 uM.
The present study investigated the potential role of selected antioxidant enzymes: superoxide dismutase (SOD) and peroxidase (POX) as biochemical markers of the impact of tropospheric ozone. Experiments were carried out in ambient air conditions with two tobacco cultivars: Bel W3 and Bel B, which are sensitive and resistant to ozone, respectively. In this study, the degree of leaf injury of the sensitive cultivar was used as an indicator of the ozone level in correlation to the enzyme activity of both tobacco cultivars. In spite of low levels of tropospheric ozone during experimental season, the increase of antioxidant enzyme (SOD and POX) activity concomitant with the increase of ozone concentration was noticed in the sensitive cultivar as well as in the resistant one. This observation is especially important for the resistant tobacco, which does not exhibit any visual effects of ozone influence. Our results could be extrapolated to other plant species (i.e. Poaceae, Fabaceae, Solanaceae, Betulaceae, Salicaceae, Pinaceae), which do not reveal visible lesions in response to ozone stress.
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